1. Field of the Invention
The present invention relates to an operated position detecting apparatus for detecting a plurality of operated positions, and electronic musical instruments using the same, such as electronic stringed instruments including an electronic guitar, guitar synthesizer and electronic violin, and electronic keyboard instruments including an electronic organ and an electronic piano.
2. Description of the Related Art
With recent, rapid developments of electronic technology and digital technology, multifarious electronic stringed instruments have been developed. The electronic stringed instruments can be classified into an electronic string rubbing instrument represented by an electronic violin and an electronic string plucking instrument represented by an electronic guitar or guitar synthesizer. The feature of such types of electronic stringed instruments or the present invention lies in that musical sounds having pitches specified by a fingering operation done to a fingerboard or a plurality of strings stretched over the fingerboard and a music is played while generating musical sounds from a musical tone generator constituted by an analog circuit, a digital circuit or the like, based on a string rubbing operation or a string plucking operation.
There are two important points in developing an electronic stringed instrument having the above arrangement. The first one is how to detect with high accuracy the status of the string rubbing or string plucking operation conducted by a player. The second one is to how to surely and quickly detect the positions on the fingerboard where the fingering operation has been executed by the player. Particularly, great efforts have been devoted to developing the latter technique of detecting the fingering initiated positions.
There are several techniques known or proposed to detect the fingering initiated positions.
The first conventional example is a fret switch system.
According to this system, ON/OFF type fret switches are embedded in a fingerboard at those positions which correspond to a number of fret positions and fingering initiated positions are detected based on the presence or absence of an ON/OFF signal output from those fret switches activated by the finger operation.
The use of this system is disclosed in, for example, U.S. Pat. No. 4,570,521 (Jeffrey Fox) issued Feb. 18, 1986.
The use of this system is also proposed in the following pending U.S. patent applications filed by the same assignee as that of the present application:
1) Ser. No. 069,612 (Yukio Kashio et al.) filed July 1, 1987 now U.S. Pat. No. 4,911,053 and corresponding Japanese Utility Model Disclosure No. 63-29193.
2) Ser. No. 094,402 (Yoshiyuki Murata et al.) filed Sept. 8, 1987.
3) Ser. No. 171,883 (Naoaki Matumoto) filed Mar. 21, 1988 and now U.S. Pat. No. 4,919,031.
4) Ser. No. 184,099 (Akio Iba et al.) filed Apr. 20, 1988 and now U.S. Pat. No. 4,817,484.
5) Ser. No. 256,398 (Akio Iba et al.) filed Oct. 7, 1988 and now U.S. Pat. No. 5,025,703.
The second conventional example is a system of detecting the resistance of a string.
According to this system, a current is supplied to a string having an electric resistance and the effective length of that string to a conductive fret in contact with the string is detected as a voltage corresponding to the resistance of this string, thereby detecting where the string is pressed.
This system is disclosed in the following patent publications:
1) U.S. Pat. No. 4,306,480 (Frank Eventoff) issued Dec. 22, 1981.
2) U.S. Pat. No. 4,468,997 (Leroy D. Young, Jr.) issued Sept. 4, 1984 and corresponding Japanese Patent disclosure No. 59-176783.
3) U.S. Pat. No. 4,653,376 (David Allured) issued Mar. 31, 1987.
4) U.S. Pat. No. 4,677,419 (Frank Meno, Assignee: University of Pittsburgh) issued June 30, 1987.
5) U.S. Pat. No. 4,630,520 (Carmine Bonanno) issued Dec. 23, 1986.
6) U.S. Pat. No. 4,702,141 (Carmine Bonanno) issued Oct. 27, 1987.
7) Japanese Patent Disclosure No. 62-174795 (M. Kondo, Assignee: Yamaha Corp.) laid open on July 31, 1987.
The third conventional example includes an electric pulse application system and a current supply system.
According to these systems, an electric pulse signal or string current is sequentially supplied to a plurality of conductive strings and this pulse signal is detected through elongated conductive frets which are in contact with the strings, thereby detecting the positions of the strings pressed.
The systems are disclosed in the following gazettes:
1) U.S. Pat. No. 3,786,167 (James J. Borell et al.) issued Jan. 15, 1974.
2) U.S. Pat. No. 3,871,247 (Arthur R. Bonham) issued Mar. 22, 1981.
3) U.S. Pat. No. 3,902,395 (William L. Avant) issued Sept. 2, 1975.
4) U.S. Pat. No. 4,038,897 (Jeffrey J. Murray et al., Assignee: Electronic Music Laboratories, Inc.) issued Aug. 2, 1977.
5) U.S. Pat. No. 4,137,811 (Ikutaro Kakehashi, Assignee: Roland Corp.) issued Feb. 6, 1979.
6) U.S. Pat. No. 4,321,852 (Leroy D. Young, Jr.) issued Mar. 30, 1982.
7) U.S. Pat. No. 4,372,187 (Arne L. Berg, Assignee: AB Laboratories) issued Feb. 8, 1983.
8) EP Disclosure No. 142,390 Al (Cintra, Daniel, et al.) published May 22, 1985 and corresponding Japanese Patent Disclosure No. 60-166992.
The fourth conventional example is an induced voltage detecting system. According to this system, a current is supplied to a plurality of conductive strings and it is discriminated from which one of coils provided in association with a plurality of conductive frets, the current is detected as an induced voltage, thereby detecting the pressed positions of strings.
Such a system is disclosed in, for example, U.S. Pat. No. 4,760,767 (Tooru Tsurubuchi, Assignee: Roland Corp.) issued Aug. 2, 1988.
The fifth conventional example is a fret detecting system with a two-layered resistive layer structure.
According to this system, a voltage pulse is sequentially applied to the individual frets of a resistive layer structure consisting of two layers having different resistances and a string current flowing through conductive strings which are in contact with the frets is detected, thereby detecting the pressed positions of the strings.
Such a system is disclosed in, for example, PCT, WO No. 87/00330 (Pyan, Paul et al., Applicant: STEPP ELECTRONICS LIMITED) laid open Jan. 15, 1987.
According to this example, each fret to be in contact with strings comprises an upper resistive layer of a high contact resistance and a lower resistive layer of a low contact resistance. The reason for employing such a structure is described as follows in WO-87/00330. With strings pressed as indicated by p and q in FIG. 31, for example, if a voltage is applied to the first fret to detect whether or not this fret is in contact with any string, a current flows across the first string through the contact resistance of the first fret and the contact of the first string with the first fret is detected by string current detecting means coupled to the first string. If the contact resistance of the fret is small, however, the current flowing across the first string also flows through the second string via the contact resistance of the second fret due to the internal resistance or the like of the string current detecting means coupled to the first string. Therefore, the string current detecting means coupled to the second string may detect the contact of the first fret with the first string. This would result in an erroneous detection of the pressed positions of strings, leading to erroneous pitch detection. It is therefore necessary to surely prevent the undesirable current flow to the wrong string.
When a pitch bend operation is performed after a string is pressed against a fret, it is necessary to detect somehow the position of the string in contact with the fret along the length thereof in order to detect the status of the pitch bend operation. In order to satisfy the above two requirements, therefore, the fifth conventional example appears to have employed the aforementioned fret structure in which each fret is constituted by the upper resistive layer of a high contact resistance and the lower resistive layer of a low contact resistance.
According to the fifth conventional example, it is suggested that circuit means for detecting the contact of frets connected to the individual strings with any string should be designed to detect a current flowing across each string. More specifically, as it is discussed that the frets should have a high contact resistance in view of a current which may flow across other strings, it is understood that the circuit means coupled to each string to detect the contact between a fret and a string, which is described in the preamble of claim 1 in WO-87/00330 relating to the fifth conventional example, should be designed to detect a current flowing across each string.
Further, it is indicated that, according to the fifth conventional example, the fret structure is provided in such a way that the first conductive layer (lower resistive layer) having the first specific resistance is deposited at the lower part of the second conductive layer (upper resistive layer) constituting a contact resistance and the first specific resistance of the first conductive layer should be large enough not to be neglected. This is said to be the essential factor in the fifth conventional example to detect not only the contact with a fret but also a pitch bend operation after the contact is made.
The sixth conventional example is a system which uses a conductive fret consisting of a plurality of conductive pieces and a plurality of strings in combination with an electronic circuit in order to detect the pressed positions of strings. This system is disclosed in, for example, U.S. Pat. No. 4,658,690 (William A. Aitken, Assignee: Synthaxe Limited) issued Apr. 21, 1987.
This electronic stringed instrument detects which sting is pressed at what fret position by a player to thereby control the pitch of a musical sound, etc. In this respect, it is considered that a player of an electronic stringed instrument plays a music by performing the ON/OFF operation of the desired switch included in a sort of a switch matrix constituted by a combination of a plurality of frets and a plurality of strings.
Accordingly, it is necessary to employ a technique of accurately detect the aforementioned string pressing operation. More specifically, it is necessary to use a technique of effectively and accurately detect the operation of an arbitrary switch in the switch matrix.
The seventh conventional example relates to such a technique but is not restricted to an electronic stringed instrument and is disclosed as a switch matrix circuit. This example is designed in such a way that a diode for preventing a signal from traveling to undesirable components is coupled to each switch located at the cross point between each row and column of a switch matrix.
The eighth conventional example relating to a similar technique is designed in such a way that a switch matrix is constituted by simple switches, the number of simultaneously operable switches is limited to one or two, and a circuit for detecting whether or not three or more switches are operated in order to prevent a malfunction. This system is disclosed in, for example, Japanese Patent Disclosure No. 62-159183 (Assignee: Yamaha Corp.).
According to the first conventional example, however, fret switches should be embedded one by one inside the neck at those positions corresponding to the individual strings between a plurality of frets, thus increasing the manufacturing cost of the neck portion. In addition, when this system is combined with a system for detecting string vibration by means of a pickup and amplifying the detected output before generating a musical sound, it is inevitable to degrade the quality of a musical sound due to the required processing of the neck portion.
According to the second conventional example, generally speaking, there is no material for the strings which have the same function as those of an ordinary guitar and have a resistance large enough to clearly show the potential difference caused by the difference between the positions of pressed frets. Further, it is difficult to design a compact circuit which permits the flow of a large current across a string having a low resistance in order to get a large potential difference from that string.
The third conventional example has the following shortcomings. If the first string 1 (#1) and second string 1 (#2) in FIG. 31 are pressed as indicated by "p" and "q" in the diagram, for example, the first string 1 (#1) contacts the (n+1)-th fret 2 (#n+1) and the (n+2)-th fret 2 (#n+2), and the second string 1 (#2) contacts the n-th fret 2 (#n) and the (n+1)-th fret 2 (#n+1). When, under this circumstance, an electric pulse signal is supplied to the second string 1 (#2) from the direction of A in the diagram, however, this signal travels through the (n+1)-th fret 2 (#n+1) to the first string 1 (#1) from the second string 1 (#2) and will be detected from the (n+2)-th fret 2 (#+2) which is not in contact with the second string 1 (#2).
According to the fourth conventional example, since a coil should be embedded in the neck for each fret, the manufacturing cost of the neck portion increases and the quality of a musical sound is deteriorated as per the first conventional example.
According to the fifth conventional example, since the upper resistive layer that will contact strings should have a high contact resistance and be made of a material having a wear-resistance high enough to resist the contact with the strings, the type of the material for this layer is restricted, thus narrowing the freedom of selecting the material for frets. Further, the circuit for detecting a large current flowing through strings from the frets comprising the upper resistive layer with a high contact resistance and the lower resistive layer with a low contact resistance should have a very complex circuit structure like a transformer, for instance. This raises the general cost of electronic musical instruments. Furthermore, to detect a pitch bend operation, it is necessary to provide, for each fret, a transformer which supplies a difference voltage for detection of the pitch bend operation to the lower resistive layer of each two-layered fret. A complicated control circuit including a feedback loop should also be provided to set a detected voltage value corresponding to the reference position of each string to 0. This feedback control requires a considerably fine initial setting and thus increases hardware components of the control circuit for detecting a pitch bend, resulting in an increase in cost.
In addition, a transformer for detecting a pitch bend needs to be embedded in the neck portion as per the first and fourth conventional examples. Accordingly, the manufacturing cost of the neck portion increases and the neck needs processed considerably, which is likely to degrade the sound quality.
According to the sixth conventional example, the flow of a current to undesirable components is prevented by causing a plurality of conductive strings supplied with a current to contact a plurality of electronically independent conductive pieces. This precaution, however, requires wiring for the number of the strings for each fret, thus increasing an electric complexity of the system for detecting a contact between frets and strings and increasing the mechanical complexity of the fingerboard as well.
According to the seventh conventional example, a diode is necessary for each switch of the switch matrix, thus inevitably increasing the switch matrix part.
According to the eighth conventional example, the number of simultaneously operable switches is restricted to 2, thus narrowing the range of electronic devices to which the switch matrix is applicable.